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The Problem

You've had the idea, you've built your emotes, you've put them all together in an animated GIF which you upload for the world to enjoy. The comments start coming in; "Sweet", "Cute", Love it", "Why is it so slow?". All well and good, apart from that last one.

So you take a closer look and either:

a) you scratch your head and think "it wasn't that slow when I built it"b) you think it looks fine but other people are still saying it's slow

So what's the problem? The answer is Stupid Browsers. Simple as that. Our browsers are just rubbish at rendering fast animated GIFs.

The Theory

An animated GIF file consists of a number of image blocks, each with it's own control block. The control block includes how long (in 1/100s of a second) the image should be displayed before moving on to the next image.

The GIF Programming Reference[1] has this to say about the frame delay:

Process each graphic in the Data Stream in sequence, without delays other than those specified in the control information.

and

Delay Time - If not 0, this field specifies the number of hundredths (1/100) of a second to wait before continuing with the processing of the Data Stream. The clock starts ticking immediately after the graphic is rendered.

All very simple, the rendering engine should simply wait for the specified delay before moving on to the next image. No exceptions! A delay of 0 should be interpreted as instantly displaying the next image and is of no practical use for creating animations. Some programs, JASC Animation Shop for example, will not allow a 0 delay. As each frame in a GIF can have it's own local colour map, some programs have even used the 0 delay to create static GIFs with more that 265 colours[2].

Imagine a series of animated GIFs that all show a progress bar. These GIFs are identical except for the frame delay. The first has a delay of 1/100 seconds, the next has 2/100, the next has 3/100, etc. When the first bar has finished the second should be half finished, the next only one third finished, etc. If you took a screenshot you should see this:

Sorry, image not available in this news article

The Truth

So that's the theory. After a number of people had mentioned problems with their animations being slower than they had build them, I decided to investigate and put together a test page containing the GIF progress bars described above. I then loaded this test page into a number of browser/OS combinations to see what happened. What I found was a remarkable example of piss poor programming.

Mozilla's rendering engine seems to have taken the line that, as screens cannot refresh faster than 90Hz, no one will ever use a delay of 1/100. So a 1/100 delay is changed to 10/100. Not what you asked for. Mozilla's answer to the 0 delay is to ignore the specification and use a delay of 10/100.

Internet Explorer is even worse. Any delay less than 6/100 is changed to 10/100. This is probably based upon the assumption that if 15fps is good enough for cartoons then it's good enough for animated GIFs.

Opera is the worst of all. Every delay below 10/100 is displayed at 10/100.

Safari is the best as far as delay cropping is concerned. It does crop below 3/100, but it crops to 3/100, not back to 10/100.

The figures below show screenshots of the test page displayed by various browsers on different platforms (this test page is available here - you may find this test works best if you download it and run it locally).

Sorry, images not available in this news article

Conclusions and Recommendations

If all the browsers followed Safari's example and just stopped making the delays faster then there would not be too much of a problem. If you ask Safari for a delay of 1/100 seconds and it delivers 3/100 then the animation might not be as fast as you wanted, but it will probably be fast enough. However, asking Internet Explorer and the Mozilla browsers for 1/100 and getting 10/100 is a significant problem.

So what delays should you use when animating GIFs? Well never 1/100 or 0; imagine what would happen if one of the popular browsers decided to honour the 0 delay! As over 2/3 of visitors[3] are using Internet Explorer I'd suggest not dropping below 6/100. If you really need to go faster than that (and I have seen a few emotes that were stunning at 2/100 in Firefox) then make it clear on your description what browsers it is suitable for. If you're feeling generous then you could always provide an alternative IE version.

very helpful thread! I found your post throught google after my 0 second delay frames were being converted to 0.10 .

I tried 0.01 and was getting the same result. After reading your thread I tried 0.03, so at least people with safari will get the full effect..and guess what. Mozilla Firefox 2.0.0.4 renders 0.03 second delays!!!

That's pretty informative and useful for me. I always thought the browsers just decided to run ALL animations on some predetermined cycling speed (like X/60 or something like that).

How about artists like =sereneworx though? His emoticons seem to be utilizing a fast animation speed without too many problems on Firefox (and perhaps Internet Explorer). Is it a similar situation with the Peacock Display emote?

Great article humpy, I already know more or less about this stuff, but it was great to see, and the bar test illustrated very well how it works, also it is good to know about the difference in browsers.

One problem I mainly have concerning frame delay times is that when I upload some, they appear faster on the Internet than they do on Fireworks. Does that have anything to do with the browser setup too?

Sorry for the late reply. I'm not too sure about Fireworks but most of the animation programs are reasonably good in their timing. The normal problem would be that it looks slower in a browser because the faster frames are given a slower delay by the browser.

If you let me know which of your animations you're having this problem with (and what browser you're using) then I'll see if I can spot any problems.

I could only find 2 that were faster online than they are on Fireworks. They are [link] and [link] The first one is set at 7/100 (because it was required to be set that way, although the project itself is reasonably slower). The second one is supposed to be just a little bit slower, enough to make a difference. I use Windows Internet Explorer 7.

I have noticed, however, that when I use Adobe ImageReady, my uploaded emotes move as fast as they do when I optimize and save them as GIFs, which is the speed I want them to be.

Well technically they are both fine apart from frame 20 in the second link. This has a delay of 0.05 which IE will interpret as 0.10 (not really significant in terms of what you are describing).

I've watched both your GIFs in FireFox 2, IE7 and Jasc Animation Shop and they all ran at similar times (with the browsers running a little slower than JAS).

It sounds as if Fireworks may be running slower than it should. You could try a little test by building an animation that has something like 100 frames with a 0.10 second delay. This should loop every 10 seconds so you could time how long it takes in Fireworks. You could also try asking some people who use Fireworks if they've seen the same problem.

Nice article, something which is important when you're dealing with quick frame delays. I've found that designing my animations to display best in the browsers from the start helps (I tried to avoid in-software playing unless I was doing something like seeing whether I was moving the objects enough, etc.) and that if I used a minimum time delay of say 0.05sec (in Imageready) it's more than smooth enough if you move things in small pixel distances.

ahhh, flash is a different kettle of fish alltogether, it will run it at exactly the speed you ask it too... if the computer is fast enough to handle it.

this is as most animations and stuff in flash is rendered in realtime, so the performance between differnent computers can vary much more than gifs in browsers.

like all things you just have to balance it all out, if you want to be really sly though you make the animation first, and just put the frames in flash, but then you have to play with your compression...

So you get to choose between live rendered and stored frames? Ohnoes... decisions

Well, animation rendering engines aren't exactly a competitive field so I'd guess there's not much development happening. For example, the MNG specs have been out for 6 years and got nowhere. The GIF format should be fine (for small scale work) if the developers bothered to follow the standard. Flash is probably the way forward as it's come from one source that produces it's own (reasonably consistent) implementations.

Oh, I see. I don't see how one can avoid it if the animation requires it though, except by changing the animation concept altogether. I mean, for instance: if I have an animation where 10/100 or even 6/100 is too slow for my purposes, then clearly I have to either take my chances with something lower or forget about it. Unless I'm missing something?

I'd say that if the animation needs it then go faster than 6/100, but make sure your description says that it will not be displayed correctly in IE.

The alternative option would be to use swf. Adobe are claiming that 98% of web users have Flash Played installed ([link]) so this is now a viable option. You just have to have a look at something like Bertie ([link]) to see how good flash can be.